1. Field of the Invention
The present invention relates to optical laser technology, and particularly to a tunable fiber ring laser with a gain clamped semiconductor optical amplifier configured to provide stable tunable-lasing over a relatively wide lasing wavelength.
2. Description of the Related Art
Tunable fiber ring lasers have found a lot of attention recently for many applications. They are widely used in wavelength division multiplexing (WDM) communication systems, laser spectroscopy and fiber optic sensor systems. The advantage offered by these laser sources is that their emission lasing wavelength can be easily tuned in a certain spectral range using different techniques. This feature can be of importance, whereby a single source can replace several laser sources. Also, erbium doped fibers (EDF) have been used as the gain medium reported using tunable fiber Bragg gratings (TFBG) for wavelength tuning in the C-band. The gratings are embedded inside a 3-point bending device for achieving wavelength tuning. The laser is tunable from 1530 nanometers (nm) to 1565 nm. Other known designs include a mode restricting intra-cavity fiber Fabry-Perot (FP) filter in the EDF based ring laser. Such a laser operates from 1533.3 nm to 1574.6 nm. The laser is predominantly tunable in the C-band than in the L-band. Further, a widely tunable erbium doped fiber ring laser based on multimode interference effect is known and is tunable from 1549 nm to 1609 nm, where tuning is more pronounced in the L-band than in the C-band. Also, a semiconductor based linear optical amplifier used as the gain medium is known, and the laser is tunable from 1507 nm to 1600 nm. Further, it is known that a tuning wavelength of 80 nm can be achieved by varying the length of the EDF in the cavity, and that the EDF length is varied from 50 m to 200 m in order to achieve a tuning range of 80 nm. Additionally, a tunable fiber ring laser is known based on a two-taper Mach Zehnder interferometer, and the laser is tuned by mechanically bending one of the two taper waists. The tuning range in the L-band is from 1564 nm-1605 nm, which was achieved by employing an L band erbium doped fiber amplifier (EDFA) in the cavity. Also, a micro-electro-mechanical system (MEMS) based in-plane FP filter has been used to demonstrate a tuning range of 35 nm in the C-band. An advantage offered by semiconductor optical amplifier based lasers is their compact size, such as when compared to their EDF based counterpart.
Thus, a tunable fiber ring laser with a gain clamped semiconductor optical amplifier addressing the aforementioned problems is desired.